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Variable Pitch Props

Discussion in 'Props, Shafts & Seals' started by Oscarvan, Aug 27, 2019.

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  1. Oscarvan, Aug 27, 2019
    #1
    Oscarvan

    Oscarvan Senior Member

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    One of the answers to the fact that a fixed prop is only efficient in a small regime, and thus every prop design is an exercise in compromise, is the variable pitch prop.

    I've seen them on airplanes, large ships and on sailboats. Not so much on power boats. One would think a planing yacht would be THE place to have one.... But I haven't heard of any.....

    Anyone know of props in the 20-30-40 inch range that are commercially available and in use? Any brand names?
  2. captholli, Aug 27, 2019
    #2
    captholli

    captholli Senior Member

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    Kamewa Ulstein CCP start in the 40 inch range I believe, France Helices and Rolls Royce Marine have CCP on the smaller side. Many motor sailors have CCP installations also but I'm not familiar with the manufactures found on them. Most if not all smaller diam. CCP will be European design and manufactured. The limitations are due to shaft and hub size where either the mechanical linkages or hydraulic lines and hub gearbox CCP components run and you cant fit this equipment in a 2-1/2 " shaft. Of course expense always is a mitigating factor as CCP units are Check book crushers vs conventional .
  3. captholli, Aug 27, 2019
    #3
    captholli

    captholli Senior Member

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    Sorry, No idea what a "CCP" is in lieu of a "CPP" , my bad...
  4. Oscarvan, Aug 27, 2019
    #4
    Oscarvan

    Oscarvan Senior Member

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    Nop prob. Seems like a serious hole in the market place..... Oh if I was 30 years younger.....
  5. Capt J, Aug 27, 2019
    #5
    Capt J

    Capt J Senior Member

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    I always thought a 2 speed transmission with very close gear ratios would pop up by someone and give you extra speed on plane. Or a 2 speed transmission with a switch with very wide gear ratios, so you'd have an idle/slow speed gear ratio for the very fast MY/SF crowd that can't idle down and a normal gear.
  6. Oscarvan, Aug 27, 2019
    #6
    Oscarvan

    Oscarvan Senior Member

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    Yup, a transmission would be cool too.... would have to be pretty hefty. Hmmm, Allison 4 speed tranny out of the back of an MCI bus on 8V-71...? May not be as crazy as it sounds....
  7. Capt Ralph, Aug 27, 2019
    #7
    Capt Ralph

    Capt Ralph Senior Member

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    There was a development of two speed clutches. Based on the Mopar 727 clutch packs (not TF8s) during the 80s.
    I remember reading the rag pages in awe.
    Not surprising, it did not catch on but it has been tried.
    Variable pitch wheels while operating is in place on some big boats to ships, just not in any budget for the rest of us.
    Some wheels were so variable, you change from forward to reverse just changing the blade angle.

    Were not talking self feathering or folding wheels here.
  8. Oscarvan, Aug 27, 2019
    #8
    Oscarvan

    Oscarvan Senior Member

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  9. PacBlue, Aug 28, 2019
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    PacBlue

    PacBlue Senior Member

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    They certainly have design/installation issues to overcome.

    The mechanics behind the hubs are cumbersome and as stated before, the Hub Outside Diameter is huge - more drag, less efficiency and all that. Not to mention that you are rotating a fixed blade design which can not be considered optimum in all speeds.

    The CPP's I have seen on vessels less than 50m are OK, maybe there is a slight benefit at lower speeds (less than planing), but they all seem to add cost, complexity and additional maintenance, not to mention special controls.

    I have looked at two similar Coast Guard vessels in the range of 45 meters, one has CPP and the other has Fixed Pitch Propeller. (FPP). Hands down, the FPP system has proven more reliable, has a better cruise and top end, is quieter and smoother at planning speeds, 20+ knots.

    Here is a company that produces some smaller products: http://www.hundestedpropeller.dk/
  10. Oscarvan, Aug 28, 2019
    #10
    Oscarvan

    Oscarvan Senior Member

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    And the gears to go with it. Snazzy. Yes, I bet it's a little over budget.